The cotton rat has been used in biomedical research since 1937, when it became the first small animal model of endemic typhus. Since then, it has been shown to be susceptible to infection by a remarkably wide spectrum of human and rodent pathogens. Of greatest current interest is its use as a model of human respiratory syncytial virus, parainfluenza virus type 3 and adenoviruses; of gene therapy of cystic fibrosis and alpha-1-antitrypsin deficiency; of filariasis; of pineal gland research; and of environmental toxicity. Use of the cotton rat, however, has been severely restricted due to lack of a commercial source of animals, an inbred cotton rat and immunologic reagents. Virion Systems, Inc. now provides inbred cotton rats commercially. The development of the reagents proposed in this grant application will greatly increase the utilization of the cotton rat as a model for a wide spectrum of human diseases.